Technical Field
This invention relates in part to processes for converting carbon monoxide- and hydrogen-containing feedstocks, e.g., synthesis gas, to oxygenated products, e.g., esters, acids, acid anhydrides and mixtures thereof, and to catalysts for said processes. This invention also relates in part to processes for converting an alcohol, ether and/or ether alcohol feedstock to oxygenated products, e.g., esters, acids, acid anhydrides and mixtures thereof, and to catalysts for said processes.
It is known that carboxylic esters, acids, anhydrides and mixtures thereof can be prepared from feedstock comprising carbon monoxide and hydrogen gases by first forming an alcohol, such as methanol, and the corresponding ether (e.g., dimethyl ether), according to the theoretical reaction:
2CO+4H2=2CH3OH⇄(CH3)2O+H2O
in the presence of a known alcohol conversion catalyst, and then separately converting the alcohol and/or ether in the presence of a known carbonylation catalyst into esters, acids, anhydrides and mixtures thereof containing one carbon atom more than the starting alcohol and ether, for example (theoretically):
CH3OH+CO=CH3COOH
or
(CH3)2O+2CO+H2O=2CH3COOH
or
CH3OH+(CH3)2O+3CO+H2O=3CH3COOH
Known two step catalytic processes for producing oxygenates are described in U.S. Pat. Nos. 5,189,203 and 5,286,900. In each of the processes described in these patents, the alcohol conversion from carbon monoxide and hydrogen is carried out in a first reaction zone wherein the alcohol, and optionally the corresponding ether, are refined to a product stream and the product stream is then passed from the first reaction zone to a second reaction zone wherein the alcohol and ether are converted by a carbonylation reaction to ester, acid, anhydride or mixtures thereof As disclosed, the useful temperature and pressure ranges for carrying out the separate reactions are different. Specifically, the alcohol synthesis reactor temperatures and pressures are selected from the ranges of from about 150xc2x0 C. to about 400xc2x0 C. and from about 70 to 3000 psig, respectively, whereas the carbonylation reactor temperatures and pressures are selected from the ranges of from about 100xc2x0 C. to about 500xc2x0 C. and about 15 to 12,000 psig, respectively.
It has been disclosed that oxygenates can be produced from a synthesis gas from rhodium catalysts. JA 62/148437 and JA 62/148438 disclose the simultaneous production of acetic acid, acetaldehyde and ethanol from a synthesis gas reacted in the presence of a rhodium catalyst pretreated with sulfur-containing compounds. JA 61/178933 discloses producing oxygenates from a synthesis gas wherein the reaction is carried out in the presence of a rhodium catalyst provided with an accelerator metal such as scandium, iridium or an alkali earth metal. JA01/294643 discloses the production of oxygenated compounds such as acetic acid in which a synthesis gas is reacted in the presence of a rhodium catalyst on a silica substrate.
The cited prior art processes for producing oxygenates from a synthesis gas have taken one of two routes: a first route wherein two separate reaction zones are usedxe2x80x94a first reaction zone to produce the alcohol, followed by separation and purification, and a second reaction zone to effectuate the carbonylation reaction to produce oxygenates, wherein the temperatures and pressures are selected from different ranges; and, a second route wherein a rhodium catalyst, contained on a substrate or treated with a specific compound (such as sulfur-containing compounds) or enhanced by an accelerator, is used to produce oxygenates and/or mixtures thereof along with aldehydes and alcohols. The first route is inefficient and capital intensive, requiring separate reaction zones, alcohol purification and complex equipment. The second route suffers from poor selectivity, resulting in a broad range of oxygenated products, because one catalytic component is being used to catalyze both reactions.
Known catalytic carbonylation processes for producing oxygenates are described in U.S. Pat. Nos. 5,218,140 and 5,330,955. Such processes involve the carbonylation of one or more alcohols, ethers and ether alcohols to esters and carboxylic acids. The processes are carried out in the vapor state over a solid catalyst comprising a polyoxometalate anion in which the metal is at least one taken from Groups 5 and 6 (such as molybdenum, tungsten, vanadium, niobium, chromium and tantalum) complexed with at least one Group 8, 9 or 10 cation (such as Fe, Ru, Os, Co, Rh, Ir, Ni, Pd and Pt).
Currently, commercial processes for the production of acetic acid from methanol and carbon monoxide employ iodide promoters which are essential to obtain an acceptable level of catalyst activity. Iodide promoters are highly corrosive, requiring the use of exotic metals in the construction of the reaction vessels and expensive processing equipment (e.g., separation and refining equipment) to recover the homogeneous promoter from the product stream.
The oxygenates industry, particularly the acetic acid industry, would benefit significantly from a process that would simplify and/or eliminate complex, expensive equipment while simultaneously enabling more control over reaction rates and product selectivity. A solution enabling these advantages would provide a highly desirable industrial advance. Improved carbonylation catalysts for making oxygenates with respect to catalyst stability and carbonylation activity and selectivity would also be a highly desirable industrial advance.
This invention relates in part to a process for converting a feedstock comprising carbon monoxide and hydrogen to a product stream comprising at least one of an ester, acid, acid anhydride and mixtures thereof which comprises reacting the carbon monoxide and hydrogen in the presence of a catalyst comprising an alcohol synthesis catalytic component and an alcohol carbonylation catalytic component, the composition of the components being different from one another, under conditions of temperature and pressure sufficient to produce said product stream. This process is preferably a gas or vapor phase reaction of synthesis gas to produce oxygenates therefrom, and is especially advantageous for the production of acetic acid and/or methyl acetate utilizing a single reaction vessel.
This invention also relates in part to a process for converting a feedstock comprising carbon monoxide and hydrogen to a product stream comprising at least one of an ester, acid, acid anhydride and mixtures thereof which comprises (a) reacting the carbon monoxide and hydrogen in the presence of a catalyst under conditions of temperature and pressure sufficient to produce at least one of an alcohol, ether, ether alcohol and mixtures thereof and (b) reacting carbon monoxide and said at least one of an alcohol, ether, ether alcohol and mixtures thereof in the presence of a catalyst comprising a solid super acid, clay, zeolite or molecular sieve under conditions of temperature and pressure sufficient to produce said product stream. This process is preferably a gas or vapor phase reaction, and is especially advantageous for the production of acetic acid and/or methyl acetate utilizing separate reaction vessels for steps (a) and (b).
This invention further relates in part to a process for converting a feedstock comprising at least one of an alcohol, ether, ether alcohol and mixtures thereof to a product stream comprising at least one of an ester, acid, acid anhydride and mixtures thereof by reacting carbon monoxide and said at least one of an alcohol, ether, ether alcohol and mixtures thereof in the presence of a catalyst comprising a solid super acid, clay, zeolite or molecular sieve under conditions of temperature and pressure sufficient to produce said product stream. This process is preferably a gas or vapor phase reaction, and is especially advantageous for the production of acetic acid and/or methyl acetate utilizing one or more reaction vessels.
This invention yet further relates in part to a multicomponent catalyst comprising (a) a first component capable of catalyzing a reaction of carbon monoxide and hydrogen to produce at least one of an alcohol, ether, ether alcohol and mixtures thereof and, (b) a second component having a composition different from that of the first component and capable of catalyzing a reaction of carbon monoxide and said at least one alcohol, ether, ether alcohol and mixtures thereof produced in the presence of the first component to produce at least one of an ester, acid, acid anhydride and mixtures thereof
This invention also relates in part to a solid catalyst for the carbonylation of a feedstock comprising at least one of an alcohol, ether, ether alcohol and mixtures thereof to a product stream comprising at least one of an ester, acid, acid anhydride and mixtures thereof, by reaction thereof in the vapor state, said catalyst selected from a solid super acid, clay, zeolite or molecular sieve.
The processes and catalysts of this invention are particularly unique in that they enable the production of oxygenates from carbon monoxide- and hydrogen-containing feedstocks or alcohol, ether or ether alcohol feedstocks in one or more reactors and in which no halides are required in the liquid or vapor phases of the feedstock streams and/or recycle streams of the processes, thus providing substantial economic benefits in the design of equipment to carry out the processes. Moreover, the multicomponent catalysts of this invention enable substantial control over the composition of the reaction product simply by varying the composition of one component of the catalyst and/or its concentration relative to the other component. Further, the processes and catalysts of this invention enable the production of oxygenates under one or more sets of reaction conditions. The carbonylation catalysts of this invention provide improved catalyst stability and improved carbonylation activity and selectivity as described herein. In a preferred embodiment, the alcohol producing reaction, i.e., step (a) above, and carbonylation reaction, i.e., step (b) above, can be carried out in separate reactors and each reactor can be operated at different reaction conditions. The product stream exiting the alcohol synthesis reactor can be fed directly into the carbonylation reactor.